JUDY WOODRUFF: This was the third and final day of official mourning in Belgium for victims of the Islamic State attacks in Brussels. And there was confirmation that two Americans were among the 31 dead. That word came as raids spread across the Belgian capital.

Malcolm Brabant has our coverage, from Brussels.

MALCOLM BRABANT: One raid centered on this residential neighborhood, where police suited up in bomb disposal outfits to enter two apartments. State TV reported two explosions. Cell phone footage also showed a raid on a bus stop, where a suspect was believed to be carrying a suitcase filled with explosives. He was shot in the leg and arrested.

MAN: He was sitting at the bus stop with his daughter. And after that, two cars, two special cars from the police coming, and they told him to stop. He tried to do something, boom, boom, two shots.

MALCOLM BRABANT: All told, there were three daytime arrests across the city, in addition to seven others overnight. All this follows Tuesday’s suicide attacks on the Brussels airport and the Molenbeek metro station. They came within days of police raids in the Molenbeek neighborhood last week that led to the capture of Paris attacker Salah Abdeslam.

Some of today’s activity happened in the nearby Schaerbeek neighborhood, where three days ago police also found a large stash of explosives. Meanwhile, Belgium’s nuclear plants added security and withdrew entry badges from some staff amid concern the plants could become terror targets.

Investigators also named a new suspect, 28-year-old Syrian Naim al-Hamed. They now believe he had some role in Tuesday’s assault. The attacks underscore the intelligence challenges across Europe with 28 countries in the European Union, each with its own security services, and communication among them muddled.

Claude Moniquet is a former French spy, and head of a security consultancy, the European Strategic Intelligence and Security Center.

CLAUDE MONIQUET, European Strategic Intelligence and Security Center: The services, police and intelligence, are overwhelmed by a threat which is not sized to Europe. We are facing thousands, thousands of possible potential terrorists. At the time of al-Qaida, for instance, we were facing maybe 500 to 1,000 people in Europe, and it was already considered a very hard threat. Today, we have at least 10 times more people to confront and to survey.

MALCOLM BRABANT: But how does the West counter the appeal of the Islamic State amongst young Muslims? Moroccan-born Rachid Benzine is a professor of Islamic studies. He says European governments must strive harder to help them integrate and give them a sense of belonging.

RACHID BENZINE, Professor, Islamic Studies at Protestant Institute of Theology (through interpreter): Our young people are not being radicalized in mosques. The phenomenon of radicalization is taking place within the family unit and with their friends and peers. We need to provide them with the tools so that our young people are sufficiently armed against the ideology facing us, because if you don’t fully integrate young people, their imagination will automatically create a symbolic identity, and people can die for that.

MALCOLM BRABANT: Such concerns were in the air today as Secretary of State John Kerry arrived in Belgium to meet with Prime Minister Charles Michel on defeating ISIS.

CHARLES MICHEL, Prime Minister, Belgium (through interpreter): With John Kerry to discuss the fight against terrorism, how is it possible to do better, how is it possible to work together in order to be more efficient?

JOHN KERRY, Secretary of State: We will not rest until we have eliminated your nihilistic beliefs and cowardice from the face of this earth.

MALCOLM BRABANT: Later, Kerry placed a wreath of flowers at a makeshift memorial for the victims at Brussels Airport.

And at Bourse Plaza, which has also become a memorial site, the Brussels Philharmonic played an impromptu tribute today to the victims. The Flemish Radio Choir joined them to finish with a performance of Beethoven’s “Ode to Joy,” a European anthem, and a hymn of hope for the future.

Away from Brussels, police in neighboring countries are on the move. In France, the authorities say that a man arrested there was in the advanced stages of plotting a new strike and had ties to the ringleader of Paris’ attacks last November. And in Germany, authorities are questioning two people who have potential links to the Brussels operation — Judy.

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